I've been reading a lot about storage solutions but I still haven't find the right answer for my problem.

We are a team of 3 editors (possible increasing to 4 or 5) on a 2 iMacs and a Macbook Pro (all from 2015). We currently have a few Raid drives which we edit from:
1 Caldigit (20TB in Raid5), 2 G-Raids (12TB and 8TB in Raid0) and 2 Lacies 2bigs (8TB both in Raid0).

We grew significantly over the last year and realised that we don't have a proper system in place for backups nor archiving. We normally have 2 copies of everything in different drives but nothing offsite, which worries me a lot.

For archiving, we are considering LTO6 but I'm still struggling to find the best way to have an onsite backup and an offsite one for the working projects.

We don't necessarily need shared storage to work from but probably it would make things easier, specially to backup everything automatically.

In a money saving perspective, I'd prefer a way of using the drives that we already have while adding something else (NAS or something else) for backups. At the moment we need something like 30TB for working projects.

This all makes sense and it seems like you're looking at the right things and asking the right questions in order to better protect your data. What connectivity is on the storage you listed? Is it all Thunderbolt?

As far as trying this without shared storage, you can do the archive side fine without shared storage; but backing up to LTO without shared storage is pretty hard especially if you want to send copies offsite. You really just need centralized LTO access to handle that without making it an onerous task.

I like the M-Tape a lot, a ton of our customers have used those and it's just a solid piece of hardware.

For trying to be budget conscious you could start with an M-Tape and some software to create LTFS archives. Then use a disk to disk backup utility (Like carbon copy cloner). Stick with LTFS so when you keep growing and want to move to a centralized backup option your existing archives will still work.

If you can push a little higher on budget, check out the ProMAX Platform Portable. It will turn Thunderbolt/USB/other Storage into shared storage, while adding a Asset Management, Backup and Archive layer. It also works with the M-Tape, but if you got both that would push you slightly over the budget you mentioned.

If you have any questions, feel free to hit me up on here or privately.

All the drives I've mentioned are Thunderbolt. The Promax solution you've mentioned seems a really good way to use the drives we already possess, however I'm not sure how far the budget will stretch.

Fundamentally, and this may seem very basic but it's something I'm still struggling to understand is how would you establish a workflow having: fast media drives/redundancy/offsite backup and archiving for 3 machines. Can I do everything with the DAS we already have and the LTO solution?